Process of manufacturing steel bodies having layers of different carbons



(No Model.)

J. PEDDER.

PROCESS 0F MANUFACTURING STEEL BODIES HAVING LAYERS OF DIFFERENT GARBONS.

Patented Oct. l5, 1889.

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UNITED STATES PATENT EEIcE.

JOHN PEDDER, OF PITTSBRG, PENNSYLVANIA.

PROCESS 0F MANUFACTURING STEEL BODIES FIAVING LAYERS 0F DIFFERENT CARBONS.

SPECIFICATION forming part of Letters Patent No. 412,893, dated. October 15, 1889. Application filed November 24, 1888. Serial No. 291,761. (No model) .T0 @ZZ whom, it may concern.:

Be it known that I, JOHN PEDDER, a resident of Pittsburg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvementin the Process of Manufacturing Steel Bodies Having Layers of Different Carbons; and I do hereby declare the following to be a full, clear, and exact description thereof.

My invention relates to the manufacture of steel ingots, blooms, or other bodies having layers containing different proportions of carbon, such as employed for the manufacture of mold-boards, shares, and other agricultural implements. These bodies of steel have generally been formed by the insertion of a slab orplate Within an ingot-mold and the pouring of steel or different carbons on one or both sides of such slab, this being the only practical Way of producing the article. As this required the "employment of crucible steel, which is necessarily expensive, the desirability of a method of forming such bodies of steel from cheaper grades of metal has long been recognized, but it has never been supplied.

The obj ect of my invention is to provide a method of forming such articles from Bessemer, open hearth, or like steel, and producing from the same the body of steel having layers or strata containing different proportions of carbon without the necessity of the preparation of the separate plate or slab of one carbon and the casting of the other metal thereto,

To this end my invention consists, generally stated, in maintaining the lower surface of a steel ingot, bloom, or slab at a temperature below that at Which carburization or decarburization can take place, covering the upper surface of the bloom With carburizing or decarburizing materials, forming a covering of loam or like substance over the bloom and treating materials, and generating a high heat above such covering, it being found that by such method I am enabled to carburize or decarburize part of the bloom and preserve in the other part thereof the original proportion of carbon contained in the bloom, so producing such body having strata containing different proportions of carbon in a comparatively short timemsay, from twenty to sixty hours,

according to the thickness of the part of the body to be acted upon and the desired proportion of carbon required in said part of the body for the purposes for which the articles to be formed therefrom are to be employedand that it can be formed at considerably less cost than the steel as produced in the old method, above referred to.

It also consists in other improvements, as hereinafter set forth.

'Io enable others skilled in the art to practice my invention, I will describe the same more fully, referring to the accompanying drawing, which represents by cross-section a furnace or oven suitable for practicing the same.

In the description of my invention I Will refer to the body of steel to be treated, Whether an ingot, bloom, slab, or other body, under the single term bloom I provide the furnace or oven d with a series of gratebars b for supporting the blooms to be acted upon so that the under surface of the blooms may be exposed to the atmosphere or to a blast or draft of air passing under the same. I may of course employ other supporting means by Which the under surface of the bloom may be maintained at a temperature below that at which carburization or decarburization can take place.

In preparing for the treatment of the bloom I take a bloom c of any desired thickness-- say of about six inches-this bloom being generally formed of Bessemer or open-hearth steel, though in some cases it may be desirable to employ crucible cast steel. The bloom is placed upon the grate-bars b, and bet-Ween the several blooms resting thereon I generally fill in a suitable substance which Will protect the bloom from the action of the carburizing or decarburizing materials, such as loam or sand, Where it can be properly supported, or other such material, this loam being in contact With the portion of the bloom which is to be protected from the treatment in the furnace, such body of material being shown at d. Above the loam I fill in the carburizing or decarburizing material Which it is desired to use-such, for example, as charcoal or like materials for carburizing, and ham mer-scale or other decarburizing material for decarburizing, this being shown at e.

Above these materials, and in order to protect them from the action of the flame and prevent the carburizing material, Where used, from burning out,I place a covering of loam, sand, or like substance, as at f, this covering confining the treating materials, and above this the body of the furnace is arranged for the combustion of fuel, it being preferred to employ gaseous fuel for the purpose, and to employ an arch or reverberatory cover or roof g, which will act to throw down the heat upon the materials contained in the furnace or oven. For general purposes I prefer to employ Va removable roof or cover-such as shownas it enables me to more easily and rapidly arrange the blooms Within the furnace and remove them therefrom, and also provides for the more rapid cooling of the furnace and the contents thereof after treatment. When so arranged, I introduce the gas and air into the oven or furnace, dand by means of the same I obtain in a short time avery high heat therein, and this heat passes rapidly down through the loam covering f, and `by heating the carburizing or decarburizin g materials surrounding the edges of and covering the upper surface of the blooms I am enabled to act upon such exposed portions of the same, and to cause the comparatively rapid carburizing or decarburizing of the steel blooms, it being found by practical experiment that the carburizing can be accomplished in from twenty to sixty hours, according to the depth of carbon required and the amount of carburization to be imparted to the face, and that in decarburizing a somewhat longer time is required.

During the treatment of the bloom by the passage of air under the same or the other cooling means employed the lower portion of the bloom is maintained at a comparatively low temperature below that at which the carburizing or decarburizing materials can act upon the steel, and consequently only the upper part thereof, which is heated `through the cover to a temperature high enough to permit such action, is acted upon by the treating materials, the lower part of the bloom being maintained by the low temperature thereof at the same carbon as when placed in the furnace. When the operation is completed, the blooms are removed, the resultant blooms having one stratum of highly-carburized or of decarburized steel, and the other stratum having the same carbon as in the original bloom.

By my invention I am enabled to produce blooms having the two strata of steel containing different proportions of carbon proper for the formation of safe-plates, agricultural implem ents, armor-plates, and other like articles, which may be formed therefrom by hammering or rolling the bloomsin the ordinary manner of reducing the same to plates or bars. The cost of treating the blooms in the manner above described is comparatively small, and as by my invention I am enabled to form these bodies of steel having strata containing different proportions of carbon from Bessemer, open-hearth steel, or other steel, the cost of which is much less than that of crucible steel, I am enabled to produce such blooms far cheaper than they can be made in the ordinary Way from rolled plates and the steel cast thereto.

Vhat I claim as my invention, and desire to secure by Letters Patent, is-

l. The herein-described method of forming bodies of steel having strata containing different proportions of carbon, consisting .in maintaining the lower surface of a steel ingot, bloom, or slab at a temperature below that at which carburization or decarburization can take place, covering the upper surface of' the bloom with carburizing or decarburizing materials, forming a covering of loam or like substance over the bloom and treating materials, and generating a high heat above such covering, substantially as and for the purposes set forth.

2. The herein-described method of forming bodies of steel having strata containing different proportions of carbon, consisting in eX- posing to the atmosphere the lower surface of a steel ingot, bloom, or slab, covering the upper surface of the bloom with carburizing or decarburizing materials, forming a covering of loam or like substance over the bloom and treating materials,`and generating a high heat above such covering, substantially as and for the purpose set forth.

In testimony whereof I, the said JOHN PED- DER, have hereunto set my hand.

JOHN PEDDER. Witnesses:

JNO. E. COBBETT, JAMES I. KAY.

TOO 

